Calculate the area of rectangles, circles, triangles, and trapezoids from their geometric dimensions.
Last updated: August 2026 | By Summa Calculator
This calculator finds the amount of two-dimensional space inside one of four shapes. Choose the shape first, then enter the dimensions that define its area.
Rectangle uses width and height. Circle uses radius. Triangle uses a base and the perpendicular height to that base. Trapezoid uses the lengths of the two parallel bases and the perpendicular distance between them.
All dimensions should use the same length unit. If the inputs are in meters, the result is in square meters; if they are in feet, the result is in square feet.
A = w × hWidth times perpendicular height.
A = πr²Radius is the distance from the center to the circle.
A = 1/2 × b × hHeight must be perpendicular to the chosen base.
A = 1/2 × (b1 + b2) × hb1 and b2 are the parallel sides.
For triangles and trapezoids, the height in the area formula is the perpendicular distance to the chosen base line. A slanted side is not automatically the height.
Using a slanted side in place of perpendicular height generally gives the wrong area unless that side actually meets the base at a right angle.
A rectangle 10 by 5 has area 50 square units.
A triangle with the same base and perpendicular height has half that area: 25 square units.
A circle with radius 0 has area 0. Zero dimensions are accepted as degenerate geometric cases; negative dimensions are rejected.
Rotating or moving a shape does not change its area.
Does it calculate irregular shapes?
Not directly. Break an irregular region into supported shapes, calculate those areas separately, and combine them as appropriate.
Does it convert units?
No. This calculator computes area from dimensions. Use an area converter when you already know the area and need a different unit.
Can I mix feet and inches in one shape?
Not safely. Convert all dimensions to the same length unit before calculating the area.
Is area the same as perimeter?
No. Area measures interior surface in square units; perimeter measures boundary length in linear units.
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